Numerous air heaters for domestic use are known, such as hairdryers, hand dryers, linen dryers, etc. These air heaters generally are of low power and operate on electricity.
Gas fired air heaters have been employed for hearing significant volumes, particularly for heating greenhouses or industrial heating.
These gas-fired heaters are of the direct-dilution type or of exchanger type.
In the art of air heating by direct dilution, the combustion gases are diluted into the air to be heated. This technique, which has a high efficiency, is exploited in the heating of greenhouses or some industrial buildings, when the renewal of air is sufficient to accept this technique. In general this technique could not be applied to heat habitable spaces. The renewal of air therein is, for obvious reasons of economy, effectively limited to 1 or 2 volumes/hour.
In heaters with an exchanger, the flue gases heat the air by means of heat-exchange walls, so that there is no direct contact between the flue gases and the air to be heated without any particular precautions. These heaters with an exchanger nevertheless exhibit several drawbacks. They are voluminous and costly and their efficiencies in terms of energy are relatively modes (often close to 70%). Furthermore, these heaters with an exchanger conventionally use blue-flame burners and therefore release significant quantities of nitrogen oxide.
The main objective of the invention is to propose a gas-fired air heater of the type with an exchanger which makes it possible to alleviate the various aforementioned drawbacks. The air heater according to the invention has an improved efficiency and releases only a very low level of nitrogen oxide into the atmosphere.
Also, the heaters with exchangers known to date offer relatively limited regulation possibilities. In effect, any modification of the flow rate of air to be heated may, in principle, be compensated for by a power adjustment of the burner, but the evolution in turbulence and in the convective-exchange coefficients disturbs the response during transient conditions.
More generally, the heating solutions currently known for ensuring hygrothermic comfort prove incapable of withstanding a disturbance. For example, in a dwelling heated by radiators (whether these are electric, or fed with hot water), a modification in reference temperature or external disturbance such as the opening of a door leads to a period during which the reference temperature is not met. Several tens of minutes, even 1 to 2 hours may elapse before the conditions of comfort are restored.
Likewise, the management of smells and of hygrometry is mainly achieved at the expense of thermal comfort.
Another objective of the invention is to propose an air heater which makes it possible to avoid these various drawbacks.